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arXiv 0905.1836cond-mat.quant-gascond-mat.other
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超冷原子费米气体中的短程关联和熵

Short-range correlations and entropy in ultracold atomic Fermi gases

Zhenhua Yu, Georg M. Bruun, Gordon Baym

摘要:

我们将超冷原子费米气体中的短程关联与整个温度下系统的熵$T$与耦合强度$-1/k_Fa$平面相关联。在低温极限下,熵主要由声子激发决定,相关系数按$T^4$增加。在BEC极限下,我们在Bogoliubov近似下计算了一个玻色子模型,以明确地显示声子如何增强费米子关联。在高温极限,我们表明,从维里展开的相关性下降为$1/T$。因此,相关性在有限温度下达到最大值。我们推断的费米气体的等熵线在$T,-1/k_Fa$平面的一般结构,并在酉,BEC和BCS限制的相关性的温度依赖性。我们的研究结果比较以及通过光缔合实验在更高的温度下的相关性的测量。

英文摘要:

We relate short-range correlations in ultracold atomic Fermi gases to the entropy of the system over the entire temperature, $T$, vs. coupling strength, $-1/k_Fa$, plane. In the low temperature limit the entropy is dominated by phonon excitations and the correlations increase as $T^4$. In the BEC limit, we calculate a boson model within the Bogoliubov approximation to show explicitly how phonons enhance the fermion correlations. In the high temperature limit, we show from the virial expansion that the correlations decrease as $1/T$. The correlations therefore reach a maximum at a finite temperature. We infer the general structure of the isentropes of the Fermi gas in the $T,-1/k_Fa$ plane, and the temperature dependence of the correlations in the unitary, BEC, and BCS limits. Our results compare well with measurements of the correlations via photoassociation experiments at higher temperatures.

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